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potmapstat(fili, filo, dbvs, dbib, dboc, samprad, maxneigh, nodatval, pixres, denstype, fldnme, datatype, statmodel)
| Name | Type | Caption | Length | Value range |
|---|---|---|---|---|
| FILI* | str | Input file name | 1 - | |
| FILO | str | Output file name | 0 - | |
| DBVS* | List[int] | Input vector segment | 1 - 1 | |
| DBIB | List[int] | Input bitmap segment | 0 - 1 | |
| DBOC | List[int] | Output raster channel | 0 - 1 | |
| SAMPRAD* | List[float] | Sampling radius | 1 - 1 | |
| MAXNEIGH | List[int] | Maximum neighbors | 0 - 1 | 1 - Default: 10 |
| NODATVAL | List[float] | No Data value | 0 - 1 | Default: 0.0 |
| PIXRES | List[float] | Output pixel resolution (m) | 0 - 2 | |
| DENSTYPE | str | Density type | 0 - 9 | POINT | ATTRIBUTE Default: POINT |
| FLDNME | str | Attribute field name | 0 - 64 | |
| DATATYPE | str | Output raster data type | 0 - 3 | 8U | 16U | 16S | 32R Default: 32R |
| STATMODEL | str | Statistical model | 0 - 25 | Default: Sum |
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FILI
Specifies the PCIDSK file that contains the input point segment.
If the projection of the point segment is different from the projection of the output raster, each point will be reprojected to the raster projection before the calculation is performed.
FILO
Specifies the name of the PCIDSK image file to receive the raster channel from the point segment. If the output file is not specified, it will be assumed to be the same as the input file. If the specified output file exists, its projection must be the same as that of the input file.
If FILO is specified but does not already exist, a new PCIDSK file will be created. By default, the georeferencing information from FILI will be copied to the new FILO. If a specified pixel X/Y resolution is given that is different from FILI, the extents of FILO will be different.
DBVS
Specifies the vector segment that contains the points to convert.
DBIB
Specifies the bitmap segment that restricts the region to process when generating the weighted average. The results will be generated inside the bitmap segment (value 1); any pixels falling outside the bitmap (value 0) will be assigned a "No Data" value.
The bitmap also defines the georeferencing of the output raster channel, including the projection, geographic extents, and resolution of the resulting output channel.
DBOC
Specifies the output raster channel to receive converted points.
If the output file already exists, this parameter must be specified and must exist. If the output file does not exist, this parameter is ignored.
SAMPRAD
Specifies the length of the sampling radius, in meters. The sampling radius is centered on each point in the raster channel to determine which points are used in the calculation.
MAXNEIGH
Specifies the maximum number of points closest to the center of the pixel and whose radii overlap the center of the pixel to be considered in calculating an output value.
When points represent statistical data values such as population or income, the number of neighboring points should be greater than when the point data represents a non-statistical and continuous nature, such as elevation.
NODATVAL
Specifies the No Data (background) value. Any output pixels that did not receive a calculated value are assigned a No Data value and are excluded from processing. This value should fall within the allowable range for the output raster type.
If this parameter is not specified, the No Data value for each channel defaults to "0.0"
PIXRES
This parameter applies only when a new output file is created; it allows you to specify a pixel resolution or size (in meters) for the output file. By default, the pixel size is taken from the georeferencing segment of the input file. The pixel size determines the number of pixels and lines in the output file. Decreasing the pixel size results in a larger output file and increased computation time.
DENSTYPE
Specifies whether to use an attribute to generate the raster, or if the statistic is based on the number of points within the sample radius.
FLDNME
Specifies the attribute field name to use to generate the raster; for example, PixelValue.
If the density type (DENSTYP) parameter is 'ATTRIBUTE', this parameter must be specified.
DATATYPE
Specifies the data type for the output image channel.
STATMODEL
Specifies the function to use to generate the output raster.
See the Details section for more information.
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This weighted-averaging technique generates a surface by applying a sampling radius to each point in the data segment. No output values are calculated for areas lying outside the sampling radius; these will be assigned a "No Data" value. The value of each raster pixel is calculated based on the value of each point whose sampling radius overlaps the center of the pixel.
You can specify the size of the sampling radius as well as the number of points closest to the center of the quad cell to be considered in the calculation of an output value Depending on the size of the radius, very different surfaces can be generated. A classification scheme can be applied to the output. This function is most appropriate for interval or ratio point data that represents a non-continuous phenomenon. Non-continuous phenomena is data typified by a high degree of variance and uneven distribution and is highly applicable to demographic and socioeconomic statistics such as population or income.
Statistical models
Sum
The Sum statistical model calculates the total of the z-values. When a constant value of 1 is used in place of a z-value, this model determines the number of points influencing the calculation of the output value.
Sum of Squared Deviations
The Sum of Squared Deviations statistical model provides a measure of the total deviation from the mean. The output value for that portion of a radius which contains only one value, indicating there is no overlap with another radius, is the No Data value.
Variance
The Variance statistical model divides the Sum of the Squared Deviations by the total number of points less 1 that influence the calculation of the output value. The output value for that portion of a radius which contains only one value, indicating there is no overlap with another radius, is the No Data value.
Standard Deviation
The Standard Deviation statistical model is the square root of the Variance. The output value for that portion of a radius which contains only one value, indicating there is no overlap with another radius, is the No Data value.
Coefficient of Variance
The Coefficient of Variance statistical model divides the Standard Deviation by the average of the z-values with the output expressed as a percentage. The output value for that portion of a radius which contains only one value, indicating there is no overlap with another radius, is the No Data value.
Standard Error of Mean
The Standard Error of Mean statistical model divides the Standard Deviation by the square root of the number of points affecting the calculation of the output value. The output value for that portion of a radius which contains only one value, indicating there is no overlap with another radius, is the No Data value.
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The point layer in segment 32 from "irvine.pix" is converted to a raster layer in a new file named "oirvine.pix". The output raster channel is of type 32R, and the sampling radius used is 100m, with pixres of 30. The statistical model used for the conversion is Sum.
from pci.potmapstat import * fili = "irvine.pix" filo = "oirvine.pix" # will be created if it does not exist dbvs = [32] # vector segment containing points dbib = [] # not using bitmap segment dboc = [1] # output raster channel samprad = [100] # sample radius (m) maxneigh = [] # default, 10 nodatval = [] # default, 0.0 pixres = [30,30] # output pixel resolution 30x30 denstype = "" # default, POINT fldnme = "" # not used if denstype=POINT datatype = '32R' # output channel type statmodel = '' # default, Sum potmapstat( fili, filo, dbvs, dbib, dboc, samprad, maxneigh, nodatval, pixres, denstype, fldnme, datatype, statmodel )
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